Modern internal combustion engines typically generate hydrocarbon emissions by evaporative means and, as a result, vehicle fuel vapor emissions to the atmosphere are regulated. For the purpose of preventing fuel vapor from escaping to the atmosphere, an evaporative emissions (EVAP) system is typically implemented to store and subsequently dispose of fuel vapor emissions. The EVAP system is typically designed to collect vapors produced inside an engine's fuel system and then send them through an engine's intake manifold into its combustion chamber to get burned as part of the aggregate fuel-air charge. When pressure inside the vehicle's fuel tank reaches a predetermined level as a result of evaporation, the EVAP system transfers the vapor to a purge canister. Subsequently, when engine operating conditions are conducive, a purge valve opens and vacuum from the intake manifold draws the vapor into the engine's combustion chamber. Thereafter, the purge canister is regenerated with newly formed fuel vapor, and the cycle can continue.
In addition to the fuel vapor recovery function, an EVAP system is often required to perform a leak-detection function. To that end, a known analog leak-detection scheme employs an evaporative system integrity monitor (ESIM) switch which stays on if the system is properly sealed, and toggles off when a system leak is detected. When the ESIM switch is toggled off, an engine control unit (ECU) detects the change and alerts an operator of the vehicle with a malfunction indicator.
In view of the above, the inventors have recognized a need for an apparatus and methodology that permits an EVAP system to accomplish its prescribed fuel evaporative emissions purge and leak detection functions in forced induction applications while reducing leak paths in the EVAP system that are potentially undetectable.